OSL and radiocarbon dating of a pre-Angkorian canal in the Mekong delta, southern Cambodia

This study presents preliminary results of research on pre-Angkorian canals near the ancient settlement of Angkor Borei in the southern Mekong delta of southern Cambodia. The canals have been mapped by aerial photograph interpretation and investigated in the field by hand auger drilling of two canal traces and trenching of one of these. Luminescence profiling through the canal infill successfully identified the base of the canal as well as revealing disturbance and mixing of the canal infill that was not apparent from visual inspection or sedimentological analyses of the infill sediments. OSL dating of the canal bed indicates excavation (or re-excavation) of the canal bed between the first millennium BC and the middle of the first millennium AD. This date is consistent with the time of initial occupation of Angkor Borei in the fourth century BC. Multiple charcoal samples with a pooled age of early fourth to early fifth century AD probably signal the onset of canal infilling. The apparent demise of the canal coincides with a major change in land-use signalled in pollen and diatom data from Angkor Borei, but this change cannot be taken to indicate de-population of the region. This tentative chronology will be refined when more canals are investigated and greater precision is achieved in OSL dating of the canals. The latter will necessitate clearer identification and separation of unbleached (older, pre-archaeological) components and bleached (younger and dating the canal digging and/or operation) components in the OSL stored dose. (C) 2003 Elsevier Ltd. All rights reserved.